LOCALIZATION OF PITUITARY ADENYLATE CYCLASE-ACTIVATING POLYPEPTIDE (PACAP) IN THE HYPOTHALAMUS-PITUITARY SYSTEM IN RATS - LIGHT AND ELECTRON-MICROSCOPIC IMMUNOCYTOCHEMICAL STUDIES

The localization of pituitary adenylate cyclase-activating polypeptide (PACAP) in the hypothalamus-pituitary system in rats was examined in light and electron microscopic immunocytochemistry using a specific an tiserum to synthetic PACAP 1-38 (R0831). In light microscopic study, i ntensely PACAP-immunostained perikarya were observed in the supraoptic and paraventricular magnocellular nucleus in the hypothalamus. In the median eminence, many immunoreactive nerve fibers were observed in th e internal layer, but a few immunoreactive terminals were noticed in t he external layer. In the pituitary gland, numerous immunoreactive ner ve fibers were observed in the posterior robe. In the intermediate rob e, moderately immunostained cells were observed, but in the anterior l obe no immunostained cells were noticed. In electron microscopic study , PACAP-immunoreactivity was examined by avidin-biotin peroxidase comp lex method. In the perikarya of the supraoptic and paraventricular mag nocellular nucleus, DAB-reaction products were distributed diffusely i n the cytoplasmic matrix, frequently attaching to the rough-surfaced e ndoplasmic reticulum. In the nerve terminals of the posterior lobe, re action products were observed among the secretory granules, but someti mes upon them. In the cells of the intermediate lobe, reaction product s were also distributed in the cytoplasmic matrix.